Polymerization of cyclic esters



United States Patent Th1s invention relates to a process for polymerizing cyclic esters and to the products resulting therefrom.

The most generally familiar Works on the polymerization of lactones are the now classical investigations of W. 'H. Carothers. For instance, Carothers was able to polymerize delta-valerolactone to poly-:delta-valerolactone by heating at 80-85 C. for a period of about 13.

days, or by contacting delta-valerolactone with potassium carbonate catalyst at a temperature of 8085 C. for a period of about days. The resulting polymers were soft waxes possessing average molecular weights of approximately 2000 which had relatively low thermal stabilities. The literature reports that attempts to polymerize gamma-buty-rolactone have been unsuccessful, and the corresponding polyester is not known. In 1934, there was reported the preparation of poly-cpsilon-caprolactone by heating epsilon-caprolactone at about 150 C. for a period of 12 hours, or by contacting epsilon-captolactone with potassium carbonate at about 150 C. for a period of 5 hours. The resulting epsilon-caprolactone polymers had melting points of about 539-55" C. and average molecular weights of about 4000. The polymers were hard, brittle waxes which could not be colddrawn into fibers. 'Bischolf and Waldon describe the transformation of glycolide under the influence of heat o a trace of zinc chloride into a polymeric solid meltirE'iTZZO C. On being distilled in a vacuum it was reconverted to the monomer melting at 8687 C. The literature also reports the polymerization of lactide at elevated temperatures to a resinous mass. A similar effect is also obtained at relatively lower temperatures by employing potassium carbonate as the catalyst.

In a broad aspect the present invention is directed to the process for polymerizing monomeric cyclic esters in contact with an organometal-lic catalyst to produce useful polyester products both the cyclic ester reagents and the organometallic catalysts being described hereinafter in a copolyme-rs, and terpolymers prepared by the practice of the instant invention are highly useful products as will become apparent at a later section herein. In addil'tion, the polymerization reaction can be conducted at lower temperatures and at faster polymerization rates heretofore unattainable in jlactone polymerization art.

Accordingly, one or more of the following objects will be achieved by the practice of this invention.

Collected Papers of Wallace H. Carothers, edited by H. Mark and G. S. Whitby, volume I. Iuterscience Publishers, Inc., New York (1940). I

F. J. van Natta, J. W. Hill and W. H, Carothers, J'our.

Amer. Chem. $00., 56, 4:55 (1934).

5 Ber. 36, 1200 (1903).

"ice

It is an object of this invention to provide a novel process for homopolyrnerizing monomeric cyclic esters to produce useful homopolymers. It is another object of this invention to provide a novel process for polymerizing an admixture containing at least two different monomeric cyclic esters to produce useful polymers. A further object of this invention is to prepare la-ctone polymers having a high degree of utility and application in the cosmetic, wax, polish, thickening, molding, coating, -etc., fields. Other objects will become apparent to those skilled in the art in the light of the instant specification.

In one embodiment the monomeric cyclic esters employed in the polymerization process of this invention can be characterized by the following formula:

wherein each R, individually, can be hydrogen, alkyl, aryl, alkaryl, aralkyl, cycloalkyl, halo, haloalkyl, alkoxyalkyl, alkoxy, aryloxy, and the like; wherein A can be an oxy (O) group, a'thio (--S-) group, a divalent saturated aliphatic hydrocarbon group, and the like; wherein x is an integer from 1 to 15 inclusive; wherein y is an integer from 1 to 15 inclusive; wherein z is an integer having a value of zero or one; with the provisos that (a) the sum of x+y+z cannot equal 3, ('b) the total number of atoms forming the cyclic ester ring does not exceed 18, preferably does not exceed 9, (c) the total number of organic substituents (such as those described for the R variables) attached to the carbon atoms contained in the cyclic ester ring does not exceed 4, preferably does not exceed 3, (d) from 2 to 4 continuously linked carbon atoms contained in the cyclic ester ring can represent a portion of a saturated cycloalipha-tic hydrocarbon nucleus which contains from 4 to 10 ring carbon atoms, and (e) the four R variables attached to any two adjacent carbon atoms contained in the cyclic ester ring can represent a portion of a fused aromatic hydrocarbon nucleus.

With reference to Formula I supra, illustrative R radical include, among others, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl, amyl, the hexyls, the heptyls, the octyls, dodecyl, octadecyl, phenyl, benzyl, tolyl, xylyl, ethylphenyl, butylphenyl, phenethyl, phenylpropyl, phenylbutyl, cyclopentyl, 2-propylcy'clohexyl, cyclohexyl, 2-rnethylcyclohexyl, cycloheptyl, chlorornethyl, chloroethyl, bromopropyl, bromobutyl, chloro, fluoro, bromo, iodo, methoxymethyl, ethoxyethyl, propoxymethyl, butoxypropyl, methoxy, ethoxy, n-propoxy, n-butoxy, isopentoxy, n-hexoxy, Z-ethylhexoxy, 3-methyloctoxy, decoxy, dodecoxy, octadecoxy, phenoxy, ethylphenoxy, propylphenoxy, dimethylphenoxy, phenylpropoxy, and the like. It is preferred that each R, individually, be hydrogen, alkyl, and/or alkoxy, and preferably still, that each R, individually, be hydrogen, lower alkyl, e.g., methyl, ethyl, u-propyl, isobutyl, and/or lower alkoxy, e.g., methoxy, ethoxy, propoxy, n-butoxy, and the like. It is further preferred that the total number of carbon atoms in the substituents attached to the cyclic ester ring does not exceed twelve. Cycloalkyl' and lower alkyl-substituted cycloalkyl radicals which have from 5 to 7 carbon atoms in the cycloaliphatic nucleus also are preferred.

In the discussion of the generic class of monomeric cyclic esters (formula I) contemplated in the process of the invention, five provisos enumerated from (a) through (e) have been set forth. Proviso (a) states that the sum of x+y+z cannot be a number equal to three. This proviso excludes cyclic ester compounds which contain five atoms in the ring such as, for example,

a gamma-butyrolactone Prior art attempts to polymerize gama-butyrolactone and the substituted gamma-butyrolactones have been unsuccessful. Attempts to polymerize the cylic esters, e.g., gamma-butyrolactones, beta-oxa-gamma buytrolactones, and the like, in the process of this invention likewise have failed. One would postulate that the thermodynamic stability of these monomeric cyclic esters which contain five atoms in the lactone ring is much greater than the corresponding polymers, and that the free energy of interconversion is exceedingly low. Proviso (c) states that the total number of organic substituents attached to the carbon atoms contained in the cyclic ester ring should not exceed four, and preferably should not exceed three. It has been observed that when the total number of organic substituents on the cyclic ester ring approached four or more, then the polymerizability of the cyclic ester monomer in the process of the invention diminished drastically. Proviso ((1) states that from 2 to 4 continuously linked carbon atoms contained in the cyclic ester ring can represent a portion of a saturated cycloaliphatic hydrocarbon nucleus which contains from 4 to ring carbon atoms such as, for example, a saturated cycloaliphatic hydrocarbon nucleus derived from cycloalkane, alkyl-substituted cycloalkane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, methylcyclopentane, methylcyclohexane, and the like. Thus, for example, the following illustrative cyclic esters would be included in the proviso:

2oxa-5,7,7trlmethylblcyclo [4.1.1]octan-3-one W. H. Carothers, G. L. Borough, and F. .T. van Natt Jo r. Amer. Chem. $00., 54, 761 (1932). a u

2-0xabicyclo[3.2.2]nonan-3-oue Proviso (e) states that the four R variables attached to any two adjacent carbon atoms contained in the cyclic ester ring can represent a portion of a fused aromatic hydrocarbon nucleus, that is, an aromatic nucleus derived from benzene, alkylbenzene, methylbenzene, propylbenzene, naphthalene, and the like. To illustrate this proviso, the following compound is depicted structurally.

2,3,4,5-tetrahydro-2-keto-benzoxep1n In the structurally depicted compound immediately above, the four R variables which were attached to the carbon atoms designated by numerals 6 and 11 now represent a portion of the fused benzene ring, namely the carbon atoms designated by the numerals 7, 8, 9 and 10. The follow ing compound further illustrates proviso (e).

2-(2-hydroxymethylphenyl)benzene carboxylic acid luctone Representative monomeric cyclic esters which can be employed as starting materials in the method of the invention include, for example, betapropiolactonc, deltavalerolactone, epsilon-oaprolaotone, 7-hydroxyheptanoic acid lactone, 8-hydroxyoctanoic acid lactone, IZ-hydroxydodecanoic acid lactone, 13-hydroxytridecanoic acid lactone, 14-hydroxytetradecanoic acid laotone, IS-hydroxypentadecanoic acid lact one, 16-hydroxyhexadecanoic acid lact-one, 17-hydroxyheptadecanoic acid lactone; the alpha, alph-a-dialkyl-beta-propiolactones, e.g., alpha,alpha-dimethyLbeta-propiolactone, alpha,alpha-diethyl-beta-propiolactone, alpha,alpha-dipropyl-beta-propiolactone, and the like; the m'onoalkyl-delta-valerolactones, e.g., the monomethyl-, m-onoethyl-, monoisopropyl-, monobutyl-, monohexyl-, mon'odecyl-, and monododecyl-delta-valerolactones, and the like; the dialkyl-delta-valerolactones in which the two .alkyl groups are substituted on the same or difierent carbon atoms in the cyclic ester ring, e.g., the dimethyl-, diethyl-, diisopropyl-, dipentyl-, and di-n-octyldelta-valerolactones, and the like; the monoalkyl-, dialkyl-,

or trialkyl-epsilon-caprolactones, e.g., the monomethyl-, monoethyl-, monoisopropyl-, monohexyl-, mono-n-octyL,

dimethyl-, diethyl-, di-n-pr.opyl-, diisobutyl-, di-n-hexyl-, trimethyl-, triethyl-, and tri-npropyl-epsilon-caprolactones, and the like; the monoalkoxyand dialkoxydeltavalerolactones and epsilon-caprolaotones, e.g., monometh0xy-, monoethoxy-, monoisopropoxy-, dimethoxy-, diethoxy-, and dibutoxy-del-ta-valerolactones and epsiloncaprol-actcnes, and the like. Further illustrative cyclic esters include 3-ethyl-2-keto-1,4-dioxane, gamm-a(1-is0- propyldmethylcyclohexyl)-epsilon-caprolactone, 3 bromo 2,3,4,4 tetrahydrobenzoxepin-Z-one, 2-(2-'hydroxyphenyl)benzene carboxylic acid lactone, -hydroxyundecanoic acid lactone, 2,5,6,7-tetrahydrobenzoxepin-Zcne, 9-oxabicyclo[5.2.2] undecan-S-one, 4-oxa-14-hydroxytetradecanoic acid lactone, alpha,alphabis(chloromethyl)-propiolactone, 1,4-dioxane-2-one, 3-n-propyl-2-keto-l,4-dioxane, 3-(2-ethylhexyl)-2-keto-'1,4-dioxane, and the like. Illustrative subclasses of cyclic esters which are eminently suitable in the process of the instant invention include the unsubstituted lactones and the oxalactones which contain from 6 to 8 atoms in the lactone ring, preferably ',delt-a-valerolactone, epsilon-caprolactone, the keto-diox- "panes, and the like; the monoand polyal kyl-substitu-ted jlac-tones and oxalactones which contain from 6 to 8 atoms in the lactone ring, preferably the monoand poly-lower alkyl-delta-valerolactones, epsilon-caprolactones, and their corresponding oxalactones wherein the alkyl substituent(s) contains from 1 to 4 carbon atoms, and the like; the monoand polyalkoxy-substituted lactones and oxalactones which contain from 6 to .8 atoms in the lactone ring, preferably the monoand poly-lower alkoxy-delta-valerolactones, epsil-on-caprolac-tones, and their corresponding oxalactones wherein the alkoxy substituent(s) contains from 1 to 4 carbon atoms.

The unsubstituted and substituted delta-valerolactones, epsilon-caprolactones, Zeta-enantholaetones, and higher niembered lactones, e.g., monoand polyalkyl-substituted delta-valerolactones, monoand polyalkoxy-substituted delta-valerolactones, mono- .and polycycloalkyl substituted deltavalerolactones, aryl-substituted, delta-valerolactones, monoand polyhaloalkyl-substituted delta-valerolactones, monoand polyalkyl-substituted 'epsilon-caprol-actones, monoand polyalkoxy-epsilon-caprola-ctones, aryl-swbstituted epsilon-caprolact-ones, monoand polyhaloalkylsubstituted epsilon-oaprolactones, monoand polyalkylsubstituted zeta-enantholactones, and various other lactones described previouslycan be prepared by reacting the corresponding cyclic ketone with an anhydrous solution comprising peracetic acid and acetone. It is desirable to add the peracetic acid solution to an excess of ketone, e.g., 5 to 1 molar ratio of ketone to peracetic acid, in a still kettle maintained under reflux. The pressure can be adjusted so as to provide a kettle temperature of, forexample, about 70 C. Acetone, acetic acid by-product, and minor amounts of ketone can be continuously removed throughout the addition period. Subsequently, the lactone product can be recovered from the still kettle by conventional techniques such as by distillation.

Stoll and Rouv report the preparation of lactones which contain up to 22 carbon atoms in the last-one nucleus by a process which comprises contacting the cone spending terminal hydroxy saturated aliphatic monocarboxylic acid with benzene-sulfonic acid catalyst in boiling benzene. These authors also report the preparation of other lactones such as 14-alky1-14 hydroxytetradecanoic acid lactone, e.g., l4-hydroxypentadecanoic acid lactone, and oxa-15-hydroxypentadecanoic acid lactone, e.g., l2- oxa-lS-hydroxypentadecanoic acid lactone. Palomaa and Tonlcola 6 teach the preparation of 3-oxa-6a'hydroxyhexanoic acid. lactone by heating the corresponding terminal 6 Helv. Chim. Acta, 18,1087 1935 0 Ben, 66, 1629 1933).

namely 2,5,-6,7-tetrahydrobenzoxepin-Z-one.

meri'c feed, is suitable.

6 hydroxy saturated aliphatic monocarboxylic acid. The preparation of 2-keto-1,4-dioxane, 3-al-kyl-2-keto 1,4-dioxane, polyalkoxysubstituted delta-valerolactone, monoand polyalkyl substituted delta-valerolaotone, alkoxya-lkyl-substituted delta-valerolac-tone, etc., is recorded by Oarothers et al. The preparation of dia-lkyl-substituted, dihalosubstituted lactone, e.g., gamma,delta-dibromo-gamma, delta-dimethyl-deltawalerolactone is reported in the literature by Levina et al. German Pat. No. 562,827 discloses the preparation of 2,3,4,5 tetrahydrobenzoxepin-Z- one whereas the literature 9 reports the position isomer,

Cycloal-kylsubstituted epsilon-caprolactone, e.g., gammaU-isoprdpyl- 4-methylcyc1ohexyl)-epsi1on-caprolactone is disclosed by Belov and Kheifits. McKay et al. have recorded the preparation of halo-substituted, halo-alkyl-substituted delta-valerolactone. The literature also reports the preparation of various other cyclic esters.

The organometallic compounds contemplated as catalysts in the process of the invention can be characterized by the following formula:

wherein M is aluminum, .indium, or gallium; wherein a is an integer having a value of 2; wherein R is a monovalent hydrocarbon radical free of ethylenic and .acetylenic unsaturation, e.g., alkyl, aryl, cycloalkyl, aralkyl, alkaryl, and the like; and wherein each R", individually, is a halo radical, e.g., chlor-o, fluoro, bromo, or iodo; alkoxy; aryloxy; or a monovalent hydrocarbon radical free of ethylenic and acetylenic unsaturat-ion, e.g., alkyl, .aryl, cycloalkyl, aral kyl, alkaryl, and the like. Illustrative monovalen-t hydrocarbon radicals include, for example, methyl, ethyl, propyl, isobutyl, sec. buty l, t-butyl, amyl, hexyl, isohexyl, Z-ethylhexyl, 3-rnethylheptyl, the octyls, the decyls, the dodecyls, the octadecyls, cyclopen-tyl, cyclohexyl, cycloheptyl, 2-met-hylcyclohexyl, l butylcyclohexyl,

2-methylcycloheptyl, phenyl, 'benzyl, ortho-, meta-, and

para tolyl, the xylyls, butylphenyl, phenethyl, phenylpropyl, phenylbutyl, trimethylphenyl, and the like. EX- empl-ary aryloxy and alk-oxy radicals include, for instance,

meth-oxy, ethoxy, propoxy, isopropoxy, sec.-b-ut-oxy, n-

butoxy, tbutoxy, hex-oxy, Z-ethylhexoxy, octoxy, dodecoxy, octadecoxy, phenoxy, phenethoxy, benzyloxy,

ortho-, meta-, and para toloxy, phenylpropoxy, phenyl- .example, t-rialkylaluminum, alkylaluminum d-ihalide, di-

alkylaluminum alkoxide, d-ialkyialurninum halide, trialkylindium, diarylindium halide, trialkylgallium, alkylgallium dihalide, .and the like. Specific examples of the organometallic catalysts include, trimethylalurninum, triethylaluminum, triphenylaluminum, tri-n-buty-laluminum, trioc-tadecylaluminum, dimethylaluminum chloride, dipropylalurninurn chloride, diisopropyl'a-luminum bromide, 'methylgalliurn dichloride, triethylgallium, trimethylgallium, trimethylindium, and the like.

The catalysts are employed in catalytically significant quantities. :In general, a catalyst concentration in the range of from about 0.001, and lower, to about 10, and higher, weight percent, based on the weight of tot-a1 mono- A catalyst concentration in the range of from about 0.01 to about 3.0 Weight percent is i See footnote 1.

8 Zuhr. Obshchei Khim, 24, 1439 (1954:). Ber., 68B, 1170 (1935).

J. Gen. Chem. USSR, 27, 1459 (1957). 11 J. Amer. Chem. Soc., 77, 56016 (1955).

preferred. A catalyst concentration in the range of from .about 0.05 to about 1.0 weight percent is highly preferred.

For optimum results, the particular catalyst employed,

.the nature of the monomeric reagent(s), the operative conditions under which the polymerization reaction is conducted, and other factors will largely determine the desired catalyst concentration.

The polymerization reaction can be conducted over a wide temperature range. Depending upon various factors such as the nature of the monomeric reagent(s) employed, the particular catalyst employed, the concentration of the catalyst, and the like, the reaction temperature can be as low as 20 C., and lower, and as high as 250 C., and higher. A suitable temperature range is from about to about 225 C. A reaction temperature in the range of from about to about 200 C. is preferred.

The polymerization reaction preferably occurs in the liquid phase, and to this extent sufficient pressure is employed to maintain an essentially liquid reaction mixture regardless whether or not an inert normally-liquid organic vehicle is employed. Preferably, the polymerization reaction is conducted under an inert atmosphere, e.g., nitrogen, butane, helium, etc. The ultimate molecular weight of the resulting polymer will depend, to an extent, upon various factors such as the temperature, the choice and concentration of the catalyst, the use .and amount of an inert normally-liquid organic 'vehicle(s), and the like.

In general, the reaction time will vary depending on the operative temperature, the nature of the monomeric cyclic ester employed, the particular catalyst and the concentration employed, the use of an inert normally-liquid 'organic vehicle, and other factors. The reaction time can vary from several minutes to several days, or more, depending on the variables illustrated above.

It is preferred to conduct the polymerization reaction in the essential absence of impurities which contain active hydrogen since the presence of such impurities tends to deactivate the catalyst and/ or increase the induction period. The minimization or essential avoidance of impurities such as water, carbon dioxide, aldehydes, ketones, etc., is highly desirable. It is also preferred that the polymerization reaction be conducted under substantially anhydrous conditions.

When polymerizing an admixture containing at least two different cyclic esters, the proportions of said cyclic esters can vary over the entire range. Broadly the concentration of each monomeric cyclic ester is in the range of from about 3 to about 97 weight percent, based on the total weight of said cyclic esters. The preferred range is from about 15 to about 85 weight percent. Admixtures containing epsilon-caprolactone and monoand/or polyalkyl-substituted epsilon-caprolaetone (including isomeric mixtures thereof) are highly preferred as starting materials in the process of the invention. Admixtures containing different monoand/or polyalkylsubstituted epsiloncaprolactones (including isomeric mixtures of the same and/or different monoand/or polyalkyl-substituted epsilon-caprolactones) also are highly preferred.

The polymers of this invention can be prepared via the bulk polymerization, suspension polymerization, or the solution polymerization routes. The polymerization reaction can be carried out in the presence of an inert normally-liquid organic vehicle such as, for example, aromatic hydrocarbons, e.g., benzene, toluene. xylene, ethylbenzene, and the like; various oxygenated organic compounds such as anisole, the dimethyl and diethyl ethers of ethylene glycol, of propylene glycol, of diethylene glycol, and the like; normally-liquid saturated hydrocarbons including the open chain, cyclic, and alkyl-substituted cyclic saturated hydrocarbons such as hexane, heptane, various normally-liquid petroleum hydrocarbon fractions, cyclohexane, the alkyl-cyclohexanes, decahydronaphthalene, and the like. If desired, a mixture of mutually miscible inert normally-liquid organic vehicles can be employed.

The process of the invention can be executed in a batch, semi-continuous, or continuous fashion. The reaction vessel can be a glass vessel, steel autoclave, elongated .metallic tube, or other equipment and material employed in the polymer art. The order of addition of catalyst and monomeric reagent(s) does not appear to be critical. A

suitable procedure is to add the catalyst to the reaction zone containing the monomeric reagent(s) and inert organic vehicle, if any. If desired, the catalyst can be in solution or suspension (in an inert normally-liquid organic vehicle). Incremental addition of catalyst to the reaction zone can be employed. If desired, the above procedure can be reversed, that is, the monomeric reagent(s) per se or as a solution or suspension in an inert organic vehicle can be added to the reaction zone containing the catalyst (or a catalyst solution or suspension). Also, the catalyst, reagent(s), and inert organic vehicle, if any, can be added to the reaction zone simultaneously. The reaction zone (be it a closed vessel or an elongated tube) can be fitted with an external heat exchanger to thus control undue temperature fluctuations, or to prevent any possible run-away reaction temperatures due to the exothermic nature of the reaction. In a continuous operation employing as the reaction zone an elongated tube or conduit, the use of one or a plurality of separate heat exchangers can be conveniently used. In a batch operation, stirring means can be provided for agitating the reaction mixture, as desired.

Unreacted monomeric reagent oftentimes can be recovered from the reaction produce by conventional techniques such as by heating said reaction product under reduced pressure. Removal of unreacted monomeric reagent(s) and/ or inert organic vehicle can be accomplished by mechanical means such as treatment of the reaction product in a Marshall mill and the like. The polymer product also can be recovered from the reaction product by washing said reaction product with an inert normallyliquid organic vehicle, e.g., heptane, and subsequently drying same under reduced pressure at slightly elevated temperatures. Another route involves dissolution in a first inert organic vehicle, followed by the addition of a second inert organic vehicle which is miscible with the first vehicle but which is a non-solvent for the polymer product, thus precipitating the polymer product. If desired, the reaction product can be dissolved in an inert organic vehicle such as acetone, and the like, followed by the addition of sufficient water to the resulting solution, said water being miscible with said inert organic vehicle but being a non-solvent for the water-insoluble polymer thereby precipitating the polymer product. Recovery of the precipitated polymer can be effected by filtration, decantation, etc., followed by drying same as indicated previously. If desired, the polymer product also can be freed of catalyst residue, if any, by extraction with dilute mineral acid such as hydrochloric acid or sulfuric acid.

The linear polyester products resulting from the process of the invention can be characterized by the following recurring structural unit:

R O tllt l Lhlf 1 wherein the variables R, A, x, y, and z have the same values as shown in FORMULA I supra. Of course, the five provisos enumerated as (a) through (c) set forth in the discussion of Formula I supra likewise apply to the structural unit designated as Formula 111 above. In addition, as intimated previously, the molecular weight of the polyester products can range from about several hundred to about several thousand. The ultimate molecular weight and properties of the polyester products will depend, in the main, upon the choice of the cyclic ester(s) and catalyst, the concentration of the catalyst, the operative conditions employed, e.g., temperature, etc., the purity of the monomeric reagent(s) and catalyst, the use and dissolved in acetone and reprecipitated in water.

9 amount of an inert normally-liquid organic vehicle, and the like.

It is readily apparent that the linear homopolymers are essentially characterized by the same recurring unit which falls within the scope of Formula III supra. The copolymers, terpolymers, etc., on the other hand, can contain as little as 1.0 weight percent, and lower, andupwards to 99 weightpercent, and higher, of the same recurring unit. Desirable polymers are those in which the weight percent of the ditferent recurring units is in the range of from about 3 to about 97. In the highly preferred copolymers the weight percent of the two different recurring units is in the range of from about 15 to about 85.

The polymers obtained by the process of the invent-ion are a useful class of polyester compounds. These polymers can range from viscous liquids to tough solids. The polymers in the range of from very viscous liquids to relatively low molecular weight, wax-like solids are useful in the preparation of cosmetics, polishes, and waxes, and as thickening agents for various lubricants. The polymers can be employed to size cellulosic material or they can be used as anti-static agents in the treatment of fibrous materials. They can also be employed as protective coatlugs, and/ or impregnants. The solid polymers are useful for the production of various shaped articles such as brush' handles, buttons, lamp bases, toys, and the like.

In passingfit should be noted that one apparent advantage afforded by the practice of the invention is the preparation of copolymers, terpolymers, etc., Whose physical characteristics can be tailor-made to fit desired fields of applications and uses. In other words, by adjusting the concentration of the monomeric charge to a particular polymerization system, copolymers, terpolyrners, etc., which cover a wide spectrum of properties and characteristics can be prepared, e.g., soft, rubbery polymers to tough, solid polymers.

Also, in the illustrative operative example below, the polymerization reaction was generally conducted under an inert atmosphere, e.g., nitrogen. The reaction vessel and contents, i.e., cyclic ester(s), catalyst, and inert organic .vehicle, if any, were maintained, usually under agitation, in a constant temperature, e.g., 90 C., or the reaction vessel containing the cyclic ester(s) was maintained, usually under agitation, in a constant temperature and subsequently the catalyst was added thereto. Since the polymerization reaction in general, was exothermic a rise in temperature was observed, e.g., 140 to 150 C. In ,severalinstances the period recorded. was the time observed in which the rotation of the mechanical stirrer ceased due to the high viscosity of the contents in the reaction vessel. In most cases the reaction vessel is left in .the constant temperature bath for an additional period of .time, e.g., 2 to 3 hours, or longer. Unless otherwise in .dicated, the examination or description of the polymeric product is conducted at room temperature, i.e., about 23 C. In general, the conversion of monomer to polymer was substantially quantitative.

EXAMPLE 1 A. To a reaction vessel maintained under a nitrogen atmosphere and which contains epsilon-caprolactone, there is charged ethylaluminum dichloride in an amount so as to give an admixture contining 0.5 weight percent 'ethylaluminum dichloride, based on the weight of said epsilon-caprolactone. The reaction vessel then .is placed in a constant temperature bath maintained at 150? C. for

.a period of 2 days. Thereafter, the reaction productis There is obtained a solid homopolymer. 1

B. In an analogous manner as above, when beta,gammadimethoxy-delta-valerolactone i substituted for epsiloncaprolactone and contacted with 1.0 weightpercent diethylaluminum ethoxide, there is obtained'a solid polymer.

EXAMPLE 2 A. To a reaction vessel maintained undera nitrogen atmosphere and which. contains epsiloncaprolactone,

there is charged a quantity of triethylauminum in an amount so as to give an admixture containing 0.6 weight EXAMPLE 3 A. To a reaction vessel maintained under a nitrogen atmosphere and which contains epsilon-caprolactone, there is charged triisopropylaluminum in an amount so as to give an admixture containing 1.0 weight percent triisopropylaluminum, based on the weight of said epsiloncaprolactone. The reaction vessel then is placed in a constant temperature bath maintained at 90 C. for a period of 92 hours. Thereafter, the polymeric product is re covered. There is obtained a tough solid.

B. In an analogous manner as above, when gamma( 1- isopropyl-4-methylcyclohexyl) epsilon caprolactone is substituted for epsilon-caprolactone and contacted with 1.0 weight percent dibutylaluminum butoxide, there is obtained a viscous liquid product.

- hours.

"caprolactone.

EXAMPLE 4 A. To a reaction vessel maintained under a nitrogen atmosphere and which contains epsilon-caprolactone, there is charged triethylaluminum in in amount so as to give an admixture containing 0.7 weight percent triethylaluminum, based on the weight of said epsilon-caprolactone. The reaction vessel then is placed in a constant temperature bath maintained at C. for a. period of Thereafter, the polymeric product is recovered from the reaction vessel. There is obtained a solid homopolymer.

B. In an analogous manner as above, when gammamethyl-delta-isopropyl-epsilon-caprolactone is substituted for epsilon-caprolactone and contacted with 1.0 weight percent triisobutylaluminum, there is obtained a very viscous liquid homopolymer.

EXAMPLE 5 To a reaction vessel maintained under a nitrogen 'atmosphere and which contains an isomeric mixture of methyl-epsilon-caprolactone, there is chargeddiethylaluminum' chloride in an amount so as to give an admixture containing 1.0 weight percent diethylaluminumchloride, based on the total weight of methyl-epsilon-caprolactone. The isomeric mixture contains, by weight, approximately 30 percent gamma-methyl-epsilon-caprolactone, and about 30 percent epsi1on-methyl-epsilon'caprolactone, and about 40 percent beta-methyland delta-methyl-epsilon-caprolactone. This isomeric lactone mixture is prepared by reacting a mixture of 2-methyl-, 3-methyl-, and 4-methylcyclohexanone with peracetic acid. The reaction vessel then is placed in a constant temperature bath maintained at C. for a period of 2 days. Thereafter, the polymeric product is recovered. There is obtained a very viscous liquid product.

EXAMPLE 6 B; In an analogous manner as above, when 2,3,4, -tetrahydrobenzoxepin-Z-one is substituted for the isomeric mixture of octyl-epsilon-caprolactones and contacted with 1.0 weight percent triisobutylaluminum, there is obtained a soft, solid polymer.

EXAMPLE 7 12 EXAMPLE 12 A. To a reaction vessel maintained under a nitrogen atmosphere and which contains zeta-enantholactone, there is charged triethylaluminum in an amount so as to give an admixture containing 1.0 weight percent triethylaluminum based on the weight of said zetaenantholactone. The reaction vessel then is placed in a constant temperature bath maintained at 90 C. for a period of 70 hours. Thereafter, the polymeric product is recovered. There is obtained a white, solid homopolymer.

B. In an analogous manner as above, when IO-hydroxyundecanoic acid lactone is substituted for zeta-enantholactone and contacted with 1.0 weight percent diethylaluminum ethoxide, essentially similar results are obtained.

EXAMPLES 13-14 In Examples 13 and 14 the procedure employed is similar to that set forth immediately preceding the operaand contacted with 1.0 weight percent trioctadecyltive examples. The pertinent data and results are realuminum, there is obtained a very viscous liquid. corded in Table 11 below.

Table II Example Catalyst Temp., Time, Description number Lactone charge 1 Catalyst concengra- 0. hrs. of polyester 13 zeta-enantholactone/7O epsi- (C2H5);A1.- 0.7 130 50 Hard solid.

lon-eaprolactone. 14 20 zeta-enantholactone/BOepsl- (CzH5)3Al 0.7 130 60 Tough solid.

lon-caprolactone.

1 Admixture of two lactones is expressed as parts by weight. 2 Weight percent catalyst, based on total weight of lactone charge.

EXAMPLE 8 A. To a reaction vessel maintained under a nitrogen atmosphere and which contains beta-methyl-delta-valerolactone (redistilled, boiling point 137 C. at 1.5 mm. of Hg; n of 1.4480) there is charged triethylaluminum in an amount so as to give an admixture containing 1.0 weight percent triethylaluminum, based on the weight of said beta-methyl-delta-valerolactone. The reaction vessel then is placed in a constant temperature bath which is maintained at 120 C. for a period of about 48 hours. Thereafter, the polymeric product is recovered. There is obtained a viscous liquid product.

B. In an analogous manner as above, when 3-oxa- 6-hydroxyhexanoic acid lactone is substituted for betamethyl-delta-valerolactone and contacted with 0.5 weight percent trioctylaluminum, essentially similar results are obtained.

EXAMPLES 9-11 In Examples 9 through 11, various copolymers are prepared by polymerizing an admixture of two lactones in the presence of triethylaluminum. The procedure employed is similar to that set forth immediately preceding the operative examples. The pertinent data and results are recorded in Table I below.

Table I Catalyst concentration 2 Time, hour Description Example of copolymer Temp., number Laetone charge 1 C 70 epsilon-eapro- 1.0 90 72 Tough solid.

lactone/30 betamethyl-deltavalerolaetone.

80 epsilon-caprolactone/20 betamethyl'deltar valerolactone.

85 epsilon-eaprolactone/l5 beta methyl-deltavalerolactone.

1. 0 90 72 Waxy solid.

1 Parts by weight.

2 Weight percent catalyst, based on total weight of lactone charge.

No'rn.Bcta-methyl-delta-valerolactone redistilled: B.P. 137 C. at 1.5 mm. of Hg: 119 of 1.4480.

EXAMPLE 15 A. To a reaction vessel maintained under a nitrogen atmosphere and which contains 2-keto-1,4-dioxane, there is charged triisobutylaluminum in an amount so as to give an admixture containing 1.5 weight percent triisobutylaluminum, based on the weight of said 2-keto-1,4-dioxane. The reaction vessel then is placed in a constant temperature bath maintained at 150 C. for a period of about 25 hours. Thereafter, the polymeric product is recovered. There is obtained a solid polymer.

B. In an analogous manner as above, when gamma (1-isopropyl-4-methy1cyclohexyl)-epsilon-caprolactone is substituted for 2-keto-1,4-dioxane and contacted with 1.0 weight percent diethylaluminum ethoxide, there is obtained a soft solid product.

EXAMPLES 16-17 In Examples 16 and 17, various copolymers are prepared by contacting, at 90 C., a mixture of epsiloncaprolactone and delta-valerolactone with 0.5 weight percent of triethylaluminum, based on the total weight of the lactone feed. The procedure employed is similar to that set forth immediately preceding the operative examples. The pertinent data and results are recorded in Table III below.

Table III Ratio of epsilou- Description Example number caprolactone to Time, hours of copolymer delta-valeroiactone 1 20:80 92 Hard solid. :20 72 Tough solid.

1 Ratio is in parts by Weight.

EXAMPLE 18 A. To a reaction vessel maintained under a nitrogen atmosphere and which contains a mixture of 50 parts by weight of epsilon-caprolactone and 50 parts by weight of mixed octyl-epsilou-caprolactones, there is charged triisobutylaluminum in an amount so as to give an admixture containing 1.5 weight percent triisobutylaluminum, based on the total weight of the lactone feed. The mixed octylcaprolactones comprises a major proportion by weight of gamma-octyland a minor proportion by weight of epsilon-octyl-epsilon-caprolactones. The reaction vessel then is placed in a constant temperature bath maintained at 90 C. for a period of 110 hours. Thereafter, the

.reaction product is dissolved in acetone and reprecipitated plary examples, but rather, the invention encompasses the generic area as hereinbefore disclosed. Various modifications and embodiments of this invention can be made without departing from the spirit and scope thereof.

What is claimed is: 1. A process which comprises polymerizing a cyclic ester characterized by the following formula:

wherein each R, individually, is selected from the group consisting of hydrogen, alkyl, aryl, alkaryl, aralkyl, cycloalkyl, halo, haloalkyl, alkoxyalkyl, alkoxy, aryloxy, a portion of an aromatic hydrocarbon nucleus which nucleus contains from 4 to carbon atoms and which is fused to the cyclic ester ring; wherein A is selected from the group consisting of an oxy group, a thio group, and a divalent saturated aliphatic hydrocarbon group; wherein x is an integer in the range of from 1 to inclusive; wherein y is an integer in the range of from 1 to 15 inclusive; and wherein z is an integer selected from the group consisting of zero and one; with the provisos that (a) the sum of x+y+z cannot equal three, (b) the total number of atoms forming the cyclic ester ring does not exceed 18, and (c) the total number of organic substituents attached to the carbon atoms contained in the cyclic ester ring does not exceed four; with from about 0.001 to about 10 weight percent, based on the total weight of cyclic ester, of an organometallic compound characterized by the following formula:

wherein M is selected from the group consisting of aluminum, indium, and gallium; wherein a is an integer having a value of 2; wherein R is a monovalent hydrocarbon radical free of ethylenic and acetylenic unsaturation; and wherein each R", individually, is selected from the group consisting of hydrogen, halo, alkoxy, aryloxy, and a monovalent hydrocarbon radical free of ethylenic and acetylenic unsaturation; under substantially anhydrous conditions; for a period of time suiiicient to produce apolymer.

2. A process which comprises polymerizing an admixture comprising at least two cyclic esters which are characterized by the following formula:

(R C' R)x R C R)y wherein each R, individually, is selected from the group consisting of hydrogen, alkyl, aryl, alkaryl, aralkyl, cycloalkyl, halo, haloalkyl, alkoxyalkyl, alkoxy, aryloxy, a portion of an aromatic hydrocarbon nucleus which nucleus is fused to the cyclic ester ring, and a portion of a saturated cycloaliphatic hydrocarbon nucleus which nucleus contains from 4 to 10 carbon atoms and which is fused to the cyclic ester ring; wherein A is selected from the group consisting of an oxy group, a thio group, and a divalent saturated aliphatic hydrocarbon group; wherein 'x is an integer in the range of from 1 to 15 inclusive;

wherein y is an integer in the range of from 1 to 15 inclusive; and wherein z is an integer selected from the group consisting of zero and one; with the provisos that (a) the sum of x-l-y'+z cannot equal three, (b) the total number of atoms forming the cyclic ester ring does not exceed 18, and (c) the total number of organic substituents attached to the carbon atoms contained in the cyclic ester ring does not exceed four; with from about 0.001 to about 10 weight percent, based on the total weight of cyclic ester, of an organometallic compound characterized by the following formula:

wherein M is selected from the group consisting of aluminum, indium, and gallium; wherein a is an integer hav- :ing a value of 2; wherein R is a monovalent hydrocarbon 25 'acetylenic unsaturation; under substantially anhydrous conditions; for a period of time suflicient to produce a polymer.

percent trialkylaluminum, based on the weight of said delta-valerolactone; at a temperature in the range of from about 0 to about 225 C.; under substantially anhydrous conditions; and for a period of time sufiicient to produce a polymer.

4. A process which comprises polymerizing an alkylsubstituted delta-valerolactone with from about 0.01 to about 3.0 weight percent trialkylaluminum, based on the weight of said alkyl-substituted delta-valerolactone; at a temperature in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time suflicient to produce a polymer.

5. A process which comprises polymerizing epsiloncaprolactone with from about 0.01 to about 3.0 weight percent trialkylaluminum, based on the weight of said epsilon-caprolactone; at a temperature in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time suflicient to produce a polymer.

6. A process which comprises polymerizing an alkylsubstituted epsilon-caprolactone with from about 0.01 to about 3.0 weight percent trialkylaluminum, based on the weight of said alkyl-substituted epsilon-caprolactone; at a temperature in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time suificient to produce a polymer.

7. A process which comprises polymerizing a monomeric lactone admixture comprising delta-valerolactone and an alkyl-substituted delta-valerolactone with from about 0.01 to about 3.0 weight percent trialkylaluminum, based on the total weight of the monomeric lactone feed; at a temperature in the range of from about 0 C. to about 225 C; under substantially anhydrous conditions; and for a period of time suflicient to produce a polymer.

8. A process which comprises polymerizing a monomeric lactone admixture comprising delta-valerolactone and epsilon-caprolactone with from about 0.1 to about 3.0 weight percent trialkylaluminum, based on the total weight of the monomeric lactone feed; at a temperautre in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time sufiicient to produce a polymer.

9. A process which comprises polymerizing a monomeric lactone admixture comprising delta-valerolactone and an alkyl-substituted epsilon-caprolactone with from about 0.01 to about 3.0 weight percent trialkylaluminum, based on the total weight of the monomeric lactone feed; at a temperature in the range of from about C. to about 225 C.; under substantially anhydrous conditions; and for a period of time sufficient to produce a polymer.

10. A process which comprises polymerizing a monomeric lactone admixture comprising epsilon-caprolactone and an alkyl-substituted delta-valerolactone with from about 0.01 to about 3.0 weight percent trialkylaluminum, based on the total weight of the monomeric lactone feed; at a temperature in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time sufiicient to produce a polymer.

11. A process which comprises polymerizing a monomeric lactone admixture comprising epsilon-caprolactone and an alkyl-substituted epsilon-caprolactone with from about 0.1 to about 3.0 Weight percent trialkylaluminum, based on the total weight of the monomeric lactone feed; at a temperature in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time sufficient to produce a polymer.

12. A process which comprises polymerizing a monomeric lactone admixture comprising an alkyl-substituted epsilon-caprolactone and an alkyl-substituted delta-valerolactone with from about 0.01 to about 3.0 Weight percent trialkylaluminum, based on the total weight of the monomeric lactone feed; at a temperature in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time sufiicient to produce a polymer.

13. A process which comprises polymerizing a monomeric lactone admixture comprising two alkyl-substituted delta-valerolactones with from about 0.01 to about 3.0 weight percent trialkylaluminum, based on the total weight of the monomeric lactone feed; at a temperature in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time suflicient to produce a polymer.

14. A process which comprises polymerizing a monomeric lactone admixture comprising two alkyl-substituted epsilon-caprolactones with from about 0.01 to about 3.0 Weight percent trialkylaluminum, based on the total weight of the monomeric lactone feed; at a temperature in the range of from about 0 C. to about 225 C.; under substantially anhydrous conditions; and for a period of time sufficient to produce a polymer.

15. The method which comprises polymerizing cyclic esters having the formula:

0 H O--O (0112),.

wherein n is an integer of from 4 to about 16 with a polymerization catalyst having the formula:

R,,-AlR',

wherein R is a radical selected from the group consisting of alkyl and aryl radicals, R is a radical selected from the group consisting of hydrogen, halogen, alkoxy and aryloxy, a is an integer of from 1 to 3, b is an integer of from 0 to 2, and a+b=3.

References Cited by the Examiner UNITED STATES PATENTS 2,808,390 10/57 Caldwell 260-78.3 2,809,958 10/57 Barnes et a1 260-78 2,822,348 2/59 Haslam 260- 2,890,208 6/59 Young et al 260-783 JOSEPH L. SCHOFER, Primary Examiner.

MILTON STERMAN, P. E. MANGAN, H. N. BUR- STEEN, Examiners. 

1. A PROCESS WHICH COMPRISES POLYMERIZING A CYCLIC ESTER CHARACTERIZED BY THE FOLLOWING FORMULA: 